When an addition-curable organopolysiloxane composition is to be cured, various curing inhibitors are used in order to adjust the curing rate and storability. As such regulators, many compounds have been already proposed. For example, Patent Literature 1 discloses organophosphorus compounds, Patent Literature 2 discloses acetylene alcohols, Patent Literature 3 discloses triallylisocyanurate, Patent Literature 4 discloses hydroxyperoxide, and Patent Literatures 5 and 6 disclose high-vinyl-content siloxanes.
Meanwhile, as a method for controlling storability and curability, for example, Patent Literatures 7 and 8 propose methods for obtaining protected curing catalyst powders by employing processes such as mixing a platinum catalyst with a silicone resin having a softening point of 40 to 200° C. and grinding or spraying the mixture with a spray dryer. Moreover, Patent Literatures 9, 10, and 11, and so on propose microencapsulation techniques for encapsulating a platinum catalyst with a thermoplastic resin.
However, such a platinum catalyst dispersed in a thermoplastic resin so quickly exhibits the catalytic activity through the thermoplastic resin melted during heat curing. For this reason, platinum catalysts soluble in organopolysiloxane compositions have been selected. Hence, in conventional techniques, a platinum catalyst diffuses from the inside of the thermoplastic resin to the inside of the siloxane composition over time, so that long-term storability is not obtained. Meanwhile, Patent Literatures described above also state the use of platinum catalysts supported on alumina, silica, carbon black, and the like. Nevertheless, the platinum catalysts soluble in siloxane compositions are merely adsorbed to the powder surface and not supported on the inorganic powder by covalent bond. Hence, there is a problem that long-term storability cannot be guaranteed for the same reason.